Fire damper with smoke seal

ABSTRACT

Smoke flow through a fire damper and particularly smoke flow about end edges of an assembly of reversely foldable damper blades is substantially reduced by leaf springs positioned adjacent the blade end edges in channels in side walls of a frame for the fire damper. The preferred leaf springs are formed from thin, elongated metal strips with a central bowed portion which projects inwardly toward the blade end edges. The leaf springs exert only a light frictional force on the end edges of the blades and hence do not impede movement of the damper blades to a curtain wall position in which the damper blades prevent fire from penetrating through the fire damper. Preferably, the leaf springs are made of stainless steel to prevent rust from developing on the leaf springs and interfering with movement of the damper blades to the curtain wall position.

United States Patent 1 [11] 3,729.,fl43

Tarnoff 1 Apr. 24, 1973 FIRE DAMPER WITH SMOKE SEAL Primary Examiner Peter M. Caun [75] Inventor: Sherwin S. Tarnoff, Northbrook, Ill. Atmmey Fitchi Even Tabin Luedeka [73] Assignee: Air Balance, Inc., Chicago, lll. [57] ABSTRACT [22] Filed: Mar. 24, 1971 Smoke flow through a fire damper and particularly Appl. No.: 127,230

smoke flow about end edges of an assembly of reversely foldable damper blades is substantially reduced by leaf springs positioned adjacent the blade end edges in channels in side walls of a frame for the fire damper. The preferred leaf springs are formed from thin, elongated metal strips with a central bowed portion which projects inwardly toward the blade end edges. The leaf springs exert only a light frictional force on the end edges of the blades and hence do not impede movement of the damper blades to a curtain wall position in which the damper blades prevent fire from penetrating through the fire damper. Preferably, the leaf springs are made of stainless steel to prevent rust from developing on the leaf springs and interfering with movement of the damper blades to the curtain wall position.

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ATTYS.

FIRE DAMPER -WI'IH SMOKE SEAL This invention relates to fire dampers and more particularly to fire dampers having an assembly of reversely foldable damper blades hinged along longitudinally extending edges thereof and movable from a stacked condition to an open curtain wall position substantially blocking the flow of air, smoke and fire through the damper.

The fire damper illustrated herein is generally of the type disclosed in U.S. Pat. No. 3,327,764 in which is disclosed a rectangular frame for installation in an air duct in either a vertical or a horizontal position. When the frame is in a vertical position, the stack of blades is located adjacent the top of the damper and is held by a strap including a fusible link. The fusible link melts when exposed to high temperature and releases the blades for unfolding, usually under the influence of gravity. The stacked blades fall and pivot into a generally fiat vertical plane thereby defining the curtain wall substantially blocking the passage of air or smoke through an opening encompassed by the damper frame.

When the fire damper is to be mounted in non-vertical position, e.g., in a horizontal position, in a duct, it may be provided with a tensioned spring which pulls the blades from the folded position, upon melting of the fusible link, to the curtain wall position substantially closing the opening in the frame. Means on the frame such as a cam lock may be used to lock the blades in the curtain wall position, thereby holding the blades against a partial return movement which would leave a gap through which fire or smoke might move.

The damper blades are usually formed with interlocking hinge portions or knuckles which not only allow the blades to pivot between the stacked and curtain wall positions but which also prevent the flow of air or smoke through these hinged connections between the blades. Even though the ends of the blades project in close proximity to the opposite side frame walls and are often guided by flanges in the side frames between these positions, smoke may flow about the ends of the blades and through spaces between theside frames and adjacent blade ends. It has been suggested, as in U.S. Pat. No. 3,273,632, that the flow of smoke about the ends of the damper blades be blocked by providing pivotally mounted blade followers biased to engage the rear edges of the blades by spring coils or loops. These spring loops were fastened to the outside of the side frames and had large rolled coils abutting the outer sides of the pivotally mounted blade followers. While such structures may prove adequate, such a method of providing end end seals adds unduly to the size and weight of the damper and is relatively expensive to manufacture and install.

For many installations other than fire dampers, rubber or elastomeric seals may be used to block air flow; but rubber or elastomeric seals will not withstand fire impinging directly thereon or very high temperatures from adjacent flames. Thus, it is necessary to use metal or other fire resistant materials; but the material used for the smoke seal can not be costly, nor can the addition thereof add inordinately to the cost of the fire damper, as cost is a most important consideration for a commercially acceptable fire damper. In addition to cost, the smoke seals should not prevent movement of the damper blades to the closed position by frictionally retarding movement thereof or stopping the blades short of the closed position. This is a problem particularly where the damper blades are dropped vertically and move to the curtain wall position solely by the force of gravity, and smoke seal elements frictionally engage and retard movement of the blades as they fall.

Of course, the failure of the blades to fall completely to the curtain wall position because of such frictional engagement with the smoke seal elements cannot be tolerated.

Accordingly, an object of the present invention is to provide a new and improved manner of substantially reducing smoke flow through fire dampers of the foregoing kind.

Other objects and advantages of the invention will become apparent from the detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a front elevational view of a fire damper embodying the novel features of the invention;

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. I;

FIG. 3 is a fragmentary, sectional view taken substantially along the line 3-3 of FIG. 1;

FIG. 4 is a view similar to FIG. 3 but with the damper blades in the curtain wall position;

FIG. 5 is a partial fragmentary, front elevational view with portions of channel forming flanges broken away to show transverse end edges of the damper blades when in the curtain wall position;

FIG. 6 is a partially sectioned view of another fire damper having springs for actuating the blades to a curtain wall position;

FIG. 7 is a partially sectioned view illustrating the locking means for the fire damper of FIG. 6; and

FIG. 8 illustrates spools on which the damper actuating springs are wound.

As shown in the drawings for purposes of illustration, the invention is embodied in a fire damper 11 having a frame 12 with an assembly 13 of metal damper blades I5 each pivotally mounted at longitudinally extending edges 16 thereof to an adjacent blade 15. The frame 12 is generally rectangular with a first pair of parallel, vertically extending side frames or walls 17 and 18 toward which project the ends of the damper blades 15 and a second pair of parallel, horizontally extending top and bottom walls 19 and 20 which extend parallel to the longitudinal direction of the damper blades 15. These walls 117, 18, I9 and 20 are joined together and encompass a rectangular opening 21 through which air may flow when the blades 15 are gathered and folded into a folded, stacked non-operative position at the top of the frame, as best seen in FIG. 1. The blades are held in this stacked condition by a securing means 23 comprising straps 24 and a fusible link 26 which, upon occurrence of excessive heat, as occasioned by a fire, melts and thereby permits the blades to open to form a curtain wall, which is partially shown in FIG. 5, closing the opening 21 and confining the fire. The blades either drop under the force of gravity or, as will be described in connection with the embodiment of the invention illustrated in FIGS. 6 and 7, are driven by a spring force to the curtain wall position.

The present invention provides means to block smoke from penetrating through spaces 28 (FIG. 3) between ends 25 of the damper blades and an adjacent frame side wall 17 or 18. Any such means to reduce smoke flow through the damper should not prevent the blades moving completely to the fire blocking curtain wall position. Also, rubber or elastomeric materials cannot be used to seal against smoke flow about the damper blades as such materials may be destroyed when impinged upon by fire or high temperature gases. Furthermore, cost is most important. Hence, the addition of means to reduce the flow rate of smoke through the damper should not add significantly to the cost of damper fabrication, nor should such means be a costly item itself.

In accordance with the present invention, smoke flow through the fire damper is substantially reduced by leaf springs 27 made of thin sheet metal positioned in vertically extending channels 29 in the side walls 17 and 18 to abut the transversely extending blade end edges 32 with a light frictional force which will not impede the blades from moving freely to the curtain wall position. More specifically, the preferred leaf springs are relatively inexpensive pieces of thin, bowed spring metal loosely positioned within the channels 29 with central bowed portions 30 projecting inwardly toward the blade end edges 32, which bowed portions can be readily deformed or flexed by the blade end edges traveling therepast. Although the leaf springs 27 do not provide a hermetic seal with the blade end edges 32, the leaf springs partially fill spaces 28 in the channel, abut the damper blades and provide a substantial reduction in the amount of smoke passing through the damper.

Each of the illustrated leaf springs 27 has longitudinally extending edges 31 bearing at spaced locations against an inner surface 33 of the side wall 17 or 18. As will be explained in greater detail, the leaf springs 27 also serve to center the damper blades with the transverse end edges 32 of the adjacent blades substantially aligned in vertical planes to prevent formation of large gaps at the blade ends 25, as would be formed, should one blade edge 32 be displaced laterally to project into one channel 29 by a distance considerably less than the distance it projects into the opposite channel 29 in the opposite side frame. Thus, when the blades are in the curtain wall position, the blades 15 are generally centered between the opposite leaf springs 27 which engage at least some blades ends and the side wall surface 33 and partially fill the spaces 28 thereby reducing the area and making a more tortuous path for any smoke attempting to flow through the damper.

Referring now in greater detail to the preferred embodiment of the invention, the preferred leaf springs 27 are severed from continuous strips of sheet metal to lengths sufficiently long to extend almost the full height of the side walls 17 and 18 to adjacent the top and bottom walls 19 and 20, with the result that the leaf springs 27 will be abutting the damper blade end edges 32 when the blades 15 are either in the folded stacked position or in the curtain wall forming position. When the blades are stacked, as shown in FIG. 2, the upper ends of the leaf springs have the arcuate bow in the central section 30 compressed and flattened by the blade ends from the arc or bow the spring metal possesses before the blades are introduced into the damper.

The preferred frame 12 and damper blades 15 are generally of the type shown in US. Pat. No. 3,327,764 and hence will not be described in detail herein. Briefly, the channels 29 are formed by bending a sheet metal strip to form a pair of reversely folded flanges 34 each formed by a pair of parallel vertically extending sections 41 and 43 abutted against each other. The flanges 34 project inwardly from and at right angles to the side walls 17 and 18. Each channel 29 is thus defined by a pair of flanges 34 and the surface 33 of the wall 17 or 18 intermediate them.

As described in the aforesaid patent, the preferred frame 12 may be made from a single piece of sheet metal stock which is appropriately notched to form corners and then bent into the rectangular shape with opposite ends of the sheet stock abutted and held together at a corner such as by welding or other fastening means. In this instance, the top and bottom walls 19 and 20 are also provided with inwardly projecting flanges 45 (FIG. 2) formed in a manner similar to that used to form the flanges 34.

In accordance with one embodiment of the invention, the uppermost damper blade 15 is pivotally mounted on pins 46 which, as best seen in FIG. 2, are secured to the side walls 17 and 18. The pins 46 are disposed adjacent the top wall 19. Alternatively, the uppermost blade may be fastened directly to the top wall 19, and the pins 46 may be dispensed with. The remaining damper blades 15 are hingedly connected in succession and will pivot to the curtain wall forming position with an inside hinge element or knuckle 47 (FIG. 2) on each blade turning in an outside hinge element or knuckle 48 formed along the longitudinally extending edge of an adjacent damper blade. The hinge knuckles are generally curved in cross section and assembled by telescopically sliding the inner hinge knuckle 47 of the smaller cross section into the larger hinge knuckle 48, all in a known manner.

As explained in the aforesaid patents, the damper blades 15 are normally held in a folded, or inoperative, position by the securing means 23 including the fusible link 26 which melts in response to exposure to a temperature environment hotter than that which is predetermined for the material used in the fusible link. Preferably, the fusible link 26 is disposed beneath the lowermost damper blade, which may be weighted, and is joined at opposite ends thereof to metal straps 24 which extend upwardly about the opposite sides of the blades to the top wall 19 to which the upper ends of the straps are fastened. Thus, securing means 23 comprises the straps 24 and the fusible link 26 and serves to hold the blades 15 until heat melts the fusible link, thereby releasing the damper blades.

When the melting of the fusible link 26 releases the damper blades 15, the blade assembly 13 opens as the blades 15 slide downwardly in the channels 29 with their blade end edges 32 sliding along the leaf springs 27. The damper blades 15 cannot escape the confines of the channels 29 as the blades 15 are longer than the distance between the inner surface 33 on one side wall and interiorly facing end of the flanges 34 on the other side wall.

When the fire damper blades fall, they extend downwardly from the upper hinge pins 46 shown in FIG. 2, which are adjacent one of the flanges 34 of the channel 29. Thus, the upper blades are disposed adjacent the dame channel flange 34 rather than being disposed centrally between the flanges 34 and abutting the center line of the arcuate portion 30 of the leaf springs 27. In such position, the damper blades may attempt force to the leaf springs to slide within the channel toward the opposite channel flange, but the blades 15 are prevented from moving behind the leaf springs, i.e., between vertical edges of the leaf springs and the adjacent flange 34 by hinge knuckles 48 abutting the flange 34. More specifically, the hinge knuckles 48 project outwardly from the plane of the blade to abut a channel flange and thereby space the flat portions of the blades from the flange and at positions to abut the bowed portions of the leaf springs 27.

With the bowed portions of the leaf springs 27 engaged by the damper blades 15 the leaf springs are maintained in vertical upright positions within the channels and they cannot fall to horizontal and inoperative positions within the damper. Although the position of the damper blades end edges 27 may vary considerably, the thin cross-section flexible leaf springs 27 will readily flex and deform to accommodate the end edges without binding the damper blades, while still appreciably filling the spaces 28 at the blade ends. To the extent the leaf springs 27 push the blade end edges 32 off the crown 30 of the springs, they push the blades toward and against the flanges 43, further reducing the area of smoke flow. While the leaf springs do not completely seal against air or smoke flow through the damper, the leaf springs do materially decrease the smoke flow therethrough.

The fire damper described above is used when the blades 15 fall and are opened by gravity; but, when the blades 15 will not fall or open with gravity, as when the frame is horizontally disposed, then the fire damper 15a illustrated in FIGS. 6-8 may be used. The damper illustrated in FIGS. 6-8 has elements identical to those above described, and these elements are identified by the reference characters used above but with the suffix a" added. The blades 15a are pulled from the stacked position of FIG. 6 into the curtain wall position by means such as a spring means 59 and are held in this position by a locking means 60, which may also be used with a gravity operated damper. Th'eillustrated spring means 59 includes a pair of spaced constant-force springs 61 each having first ends connected by fasteners 63 to the opposite ends 25a of the closest one of the damper blades. The blades are held in a stacked folded condition against the force of the springs 61 by the securing means 23a until the link 26a melts.

The preferred locking means 60 is of the type disclosed in U.S. Pat. No. 3,327,764. It has a cam notch 62 for abutting and interlocking with an edge 63 of one of the movable blades 15a. In operation, the leading edge 64 of the blade, to which the springs 61 are attached, is pulled by the springs to strike an upwardly inclined cam surface 67 and the leading blade edge 64 is cammed upwardly alongcam surface 67 to abut an end wall 68 of the bottom wall a, at which time the trailing end of the blade enters the notch 62 and prevents any rebound or return movement of this blade.

The preferred springs 61 are constant-force springs which are coiled about take-up spools 69, as best seen in FIG. 8, mounted on shafts 70. Each shaft is supported at one end on a bracket 71 and at its other end on a side wall 17a or 180. The brackets 71 are rigidly secured to the side walls at legs 73. By having two such springs, the blades are pulled with an even force to slide along the leaf springs 27a to the curtain wall position shown in FIG. 6.

The blades 15a are thus locked in this extended curtain wall position blocking the opening 210, with the end edges 32a of the blades abutting the leaf springs 27a. The leaf springs 27a yield and readily deform as the blade end edges 32a slide therealong and as the leading blade is cammed in a lateral direction by the cam surface 67. The blade end edges 32a hold the leaf springs 27a in the channels 29a against falling inwardly therefrom. The leaf springs 27a thus serve to take up space and to cause smoke to flow through smaller cross sectional cracks and through tortuous paths before flowing through the damper. The blades may be manually returned from this curtain wall position to the stacked position by lifting the trailing end 63 of the locked blade upwardly from the locking notch 62 and pulling the blades rightwardly, as seen in FIG. 7, against the force of the springs 61 and then fastening a new fusible link 26a to the free ends of the straps.

As the fire damper blades may be held in the stacked condition for years without movement and the leaf springs may be exposed to air borne moisture flowing through the fire damper, the leaf springs are subject to rusting which might interfere with or prevent sliding movement of the blades along the leaf springs to the curtain wall position. To prevent interference with proper operation of the fire damper because of such rusting, the illustrated leaf springs 27 may be made of stainless steel which will not readily rust. By having a small cross-sectional thickness for the leaf springs, e.g., about 0.01 inch, the stainless steel leaf springs 27 have sufficient flexibility to accommodate satisfactorily the sliding movement of the damper blades therealong.

From the foregoing, it will be seen that simple elongated leaf springs may be positioned in the space between end edges of the damper blades and the adjacent sidewalls for the damper frame. These leaf springs may be merely inserted into channels within the side frames without concern as to close tolerance fits or precise positioning thereof which would add to the cost of fabrication of the unit. The leaf springs are also formed of inexpensive material and deform readily to permit sliding of the blade edges therepast while conforming generally to and against the blade end edges. The leaf springs thus partially fill the space and reduce the flow of smoke through the damper. Additionally, the leaf springs serve to center the damper blades between the side walls of the frame.

While a preferred embodiment has been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A fire damper comprising a frame having a pair of side walls and top and bottom walls joined to said pair of side walls and encompassing an opening through which air may flow, a plurality of elongated metal damper blades each having a flat, planar central portion, hinge elements formed on parallel longitudinally extending edges of said damper blades and projecting outwardly from said flat, central blade portions and hingedly interconnecting said damper blades, said damper blades being reversely foldable to a stacked condition to permit air to flow through said opening and movable from said stacked condition to an unfolded curtain wall position in which the blades define a curtain wall substantially closing the opening in said frame, inwardly projecting flanges on each of said pair of side walls spaced to guide ends of said damper blades therebetween in their travel to the curtain wall position, a first one of said blades secured to said frame at said top wall, releasable securing means to hold said blades in said stacked condition and releasable to allow said damper blades to move to close substantially said opening, a one-piece, metal leaf spring loosely disposed between said inwardly projecting flanges at each of said pair of side walls, said leaf springs extending substantially the length of said opening and positioned adjacent transverse end edges of said damper blades to abut the same and limit the flow of smoke about the ends of said damper blades and between the latter and said pair of side walls, each of said leaf springs being elongated and having a central portion bowed convexly toward said damper blade and spaced from an adjacent side wall of said frame, longitudinally extending edges on said leaf springs abutting inner surfaces of said side walls adjacent said inwardly projecting flanges, said leaf springs urging said damper blades toward an adjacent one of said inwardly projecting flanges, said hinge elements including inner and outer hinge elements telescoped together with the outer hinge elements adapted to abut said flanges and to space the flat central portions of said damper blades from engagement with said flanges, said flat central portions of said damper blades being disposed intermediate the longitudinally extending edges of the leaf springs when the damper blades are in a curtain wall position whereby the leaf springs are retained in position in the frame to reduce the flow of smoke through the damper, said leaf springs being positioned opposite each other and centering the damper blades therebetween by resisting any attempted lateral displacement of a damper blade along its longitudinally extending hinged connection with an adjacent damper blade.

2. A fire damper in accordance with claim 1 in which said leaf springs are formed of stainless steel to prevent rusting thereof and a resulting interference with movement of said damper blades to the curtain wall position. 

1. A fire damper comprising a frame having a pair of side walls and top and bottom walls joined to said pair of side walls and encompassing an opening through which air may flow, a plurality of elongated metal damper blades each having a flat, planar central portion, hinge elements formed on parallel longitudinally extending edges of said damper blades and projecting outwardly from said flat, central blade portions and hingedly interconnecting said damper blades, said damper blades being reversely foldable to a stacked condition to permit air to flow through said opening and movable from said stacked condition to an unfolded curtain wall position in which the blades define a curtain wall substantially closing the opening in said frame, inwardly projecting flanges on each of said pair of side walls spaced to guide ends of said damper blades therebetween in their travel to the curtain wall position, a first one of said blades secured to said frame at said top wall, releasable securing means to hold said blades in said stacked condition and releasable to allow said damper blades to move to close substantially said opening, a one-piece, metal leaf spring loosely disposed between said inwardly projecting flanges at each of said pair of side walls, said leaf springs extending substantially the length of said opening and positioned adjacent transverse end edges of said damper blades to abut the same and limit the flow of smoke about the ends of said damper blades and between the latter and said pair of side walls, each of said leaf springs being elongated and having a central portion bowed convexly toward said damper blade and spaced from an adjacent side wall of said frame, longitudinally extending edges on said leaf springs abutting inner surfaces of said side walls adjacent said inwardly projecting flanges, said leaf springs urging said damper blades toward an adjacent one of said inwardly projecting flanges, said hinge elements including inner and outer hinge elements telescoped together with the outer hinge elements adapted to abut said flanges and to space the flat central portions of said damper blades from engagement with said flanges, said flat central portions of said damper blades being disposed intermediate the longitudinally extending edges of the leaf springs when the damper blades are in a curtain wall position whereby the leaf springs are retained in position in the frame to reduce the flow of smoke through the damper, said leaf springs being positioned opposite each other and centering the dampEr blades therebetween by resisting any attempted lateral displacement of a damper blade along its longitudinally extending hinged connection with an adjacent damper blade.
 2. A fire damper in accordance with claim 1 in which said leaf springs are formed of stainless steel to prevent rusting thereof and a resulting interference with movement of said damper blades to the curtain wall position. 